Electromagnetic drive



Dec. 1, 1942.

C. T. HIBBARD ELECTROMAGNETIC DRIVE Filed April 10, 1940 2 Sheets- Sheet 1 Charles T Hibbard Dec. 1, 1942. C.'T. HIBBARD 2,303,361 I ELEC'PROMAGNETIC DRIVE Filed April 10, 1940 2 Sheets-Sheet 2 Charles "[1 Hibbard WCM Patented Dec. 1, 1942 UNITED STATES PATENT OFFICE ELECTROMAGNETIC DRIVE Charles T. Hibbard, Minneapolis, Minn., assitnor to Electric Machinery 'apolis, Minn.

Mfg. Company,

Minne- Application April 10, 1940, Serial No. 328,936

Claims.

A still further object of the invention resides in providing an electromagnetic drive in which the .two relatively rotatable members, when operating at substantially the same -speed,.rcquire no electric energization.

*A feature of the invention resides in providing an electromagnetic drive in which the two relatively rotatable members are connected together through a clutch having one or'more movable clutch elements operated by centrifugal force to effect the desired connection.

An object of the invention resides in providing electromagnetic means for disengaging the clutchelements. g Another object of the invention resides in providing one of the members with an element having an annular friction surface and the other member with one or more shoes having clutch elements adapted to be moved into engagement with said surface by centrifugal .force.

A feature of the invention resides in providing electromagnetic means acting upon said shoes for disengaging the clutch elements thereof from said friction surface.

A feature of theinvention resides in providing a single electromagnet for operating upon all of said shoes to procure disengagement from said friction surface.

A feature of the invention resides in mounting the shoes so that they float and readily adapt themselves to the friction surface so as to-procure uniform pressure upon thessurface throughout the area of each shoe.

Other objects of the invention reside in the novel combination and arrangement of parts and in the details of construction hereinafter illustrated and described.

In the drawings:

Fig. 1 is a longitudinal elevational sectional view of an electromagnetic drive illustrating an embodiment of my invention.

Fig. 2 is an elevational sectional view of the electromagnetic drive taken on line 2-2 of Fig.1.

Fig. 3 is a fragmentary elevational sectional view taken on line 33. of Fig. 1 with a portion of the structure removed.

Fig. 4 is a plan view of the structure shownin Fig. 3.

Fig. 5 is a cross sectional view taken on line 55ofFig.3.

Fig. 6 is a cross sectional view taken on line 6-6 of Fig. 3.

In the drawings I have showna form of my invention which utilizes two rotatable members 2i and 22 which are co-axially disposed and which are rotatable relative to one another. The member 2| is driven from the source of mechanical power and the member 22 drives the load connected to it. The member 2| is mounted on a shaft 23, while the member 22 is mounted onanother shaft 24. These shafts are respectively journaled in bearings 25 and 26 carried by standards 21 and 28 mounted on a base 29. The twoshafts 23 and 24 are concentric. In the drawin s only one bearing has been shown for each shaft. In practice the bearings of theload and the source of mechanical power may be used to further support the respective shafts. If this becomes impractical it may be readily comprehended that additional bearings may be used if found desirable. The specific construction of the members 2| and 22 will now be described in detail.

The member 2| is constructed with a hub 3| which is keyed to the shaft 23; This hllb'lS polygonal in form, having a number of faces 32 extending about the periphery thereof.- these faces are formed dove-tailed slots 33. Attached to the hub 3| are a number of laminated poles 34, each of which has a body-15 and a pole tip 36 at the outermost portion thereof.

Each of these Poles is further"'constructed ..with

a. dove-tailed tongue 31 which is receivedin one of the slots 33 whereby the pole is afflxed to the hub 3i. The poles and the-hub 3| constitute the core structureof therevoluble member 2| which is indicated in its entirety by the reference numeral 30. Thenumber of poles employed depends upon the speed at which the driven member of tlfe electromagnetic drive is to be operated. I have found that highly satisfactory results are produced where the number of poles are the same as used with a synchronous motor of corresponding speed and operating from a cycle source of electric power.

The windings of the member 2| are constructed as follows: On each of the poles 34 is mounted poles.

gether in reverse relation so that alternate poles are of like polarity and so that the intervening but of a ing therefrom is that flue adjustment of riphery thereof a coil 42. Inasmuch as all of the coils are identical in construction, the description thereof will not be repeated and only the coil shown on the pole illustrated in cross section will be described. Mounted on the pole body 35is a spool 38 of insulating material which has ends 39 and 4| fitting against the face 32 of the hub 3| and against the inner surface of the pole tip 36. On the spool 38 and between the ends 39 and M iswound' the coi1 42 which is constructed of insulated copper wire. This coil is preferably constructed tapered at its inner end to provide sufficient space for ventilation between the coils on the respective The various coils 42 are connected topoles are also of the same polarity polarity opposite to that of the other poles.

The ends of the coils 42 are connected to two collector rings 43 and 44 which are mounted on an insulating ring 46 secured to the hub 3| of the member 2I., These rings have contacting therewith brushes 41 and which are carried by brush holders 49 attached to the bearing 25 and 48 are connected to a source The brushes 41 of direct current and the amount of current flowcontrolled by a rheostat' con nected in series in this lead. -By-means of this construction any with the lead from the brush 41,'the rheostat not being shown in the drawings." A suitable switch, not shown, is alsonconnected desiredamount of current may be supplied to the coils 42 so that the thereby canbe-varied, as required. A rheostat having a large number of taps may be used so coils 42 may be had. The cured with a coarse and a. known construction ship, the rheostats able.

best results are pm The member 22is provided with a hub. 5| which has a ring: spider 52 connected therewith and isp This hub is mounted on the shaft 24 and iskeyed thereto. The spider '52 is constructed at its outer end with a-rabbet 53' in which is mounted'an annular frame "54.; to the spider 52 by-means suing outwardly therefrom,

Said frame is secured of cap screws 55 which extend through said spider and are screwed into the frame. frame 54 has ribs 56 formed upon the inner pereceive the core structure 51 of the member 22. Core structure 51 is annular in form and is constructed in three sections 9|, I52 and 63 which are'held in spaced relation by means of spacers 541 The core structure 51 flts snugly within the ribs 56 and is held attached thereto by means of annular end plates 55 and 65 which are welded to the said ribs 56. I

Associated with the core structure 51 is a of a number of bars 69 which are disposed in suitable slots in the various core sections 6|, 62 and.63. These bars are connected together at their ends exteriorly of the core structure by means of end rings 12. The number of bars used may be determined in accordance with the usual practicein the design of induction motors.

For the purpose of maintaining concentricity between the rotatable members 2| and 22 the end of the shaft is reduced in diameter, as desi nated at It, to receive the inner race of a ball bearing 8!. 82 formed in the hub 3| at the endof shaft 23.

field strength produced The which are accurately bored to This bearing is mounted in a recess thefleld current in the finerheostat of well]. connected in .seriesrelation- I being independently adjustto :of the annular frame 54,

arcuate shoes 99 which are By means of this construction the two shafts are maintained concentric within the electromagnetic drive so that the air gap between the core struc-. ture 51 and the core structure remains constant; 4

In conjunction with the two rotatable members 2| and 22, I employ a clutch which I have indicated in its entirety by the reference numeral 83. This clutch utilizes a spider 84 provided with a hub 85 relatively flat. The hub 95 is secured to the hub 3| by means of cap screws 85. The spider 84 includes an annulus 81 which is formed with a perimetrically extending groove 88 by means of which the said annulus becomes U-shaped in cross section. This forms in the annulus two flanges 9| and 92 with an inner connecting portion 93 there-between. The annulus 81 is disposed in proximity to the inner portion which portion is indicated by the reference numeral 94 and has the form of a ring with an inner friction surface 95.

Secured to the flanges 9| and 92 of the annulus 81 at spaced intervals along the same are pairs of lugs '96. These lugs are set into recesses 91 formed in the said flanges and are secured in place by means of cap screws 98 threaded into said flanges. By means of the recesses 91, the lugs 96 are held from movement in a circumferential direction. The lugs 96 are preferably constructed of brass or some other suitable non-' magnetic material for a purpose to be presently explained.

Between the lugs 96 are provided a number of best shown in Figs. 3, 4, 5-and 6. Inasmuch as all of these shoes are identical in construction only the shoe illustrated in Figs. 5 and 6 will be described in detail. This shoe consists of a body I00 having an outer arcuate part IOI and an inner arcuate part I02. The

curvature of the inner surface I01 of the inner. part surface I08 of the flanges 9| I02 of shoe 99 is the same as the outer and 92. These shoe parts are secured together by means of screws squirrel cage winding I31. This winding consists I05 which extend through the ,threaded into the part 'shoe 99 overlies the outer flanges 9| and 92.

. formed on the ends part I02 and are IOI. The part I02 of periphery of the two The part IOI of said shoe has thereof ears I04 which flt in between the pairs of lugs 96. The shoes 99 are of'such length that the ends of the parts j IN and I02 thereof flt freely against the lugs 90. By means of this are' free to move radially.

Attached to the part IOI of shoe 99 is a facing friction surface 95 of the ring 94.

. In order to compensate for wear of the facings I05, the body of the shoe 99 is constructed with the ,two parts IN and I02 previously referred to. As the surface I09 of facing I05 wears, shims such as indicated at IIO, are placed between the parts It" and I02. Thus the outer surface of the facing I05 is brought into the desired proximity to the friction surface of the ring 94.

construction, the shoes are. held from axial and peripheral movement b ut Inthe construction ofi thei shoesfflycerta n ofthe shoes are made of diiierent weightsthan; theremaining shoes. This may be accomplished I by increasing ordecreasing the width .oixthe ShOET bodies or by drilling. outportions of the same The purpose ofso constructing the shoes willbe I subsequently explained in detail.

Within the groove as m the annumsci is 2,308,361 -1; 1 i 3 ,annulus 81 .is removed and centrifugal force throws {the shoes 99 outwardly bringing the surfaces I09 oftheffacings I into engagement with f the frictionsurface 95 of ring 94. This produces Y '.a. clutching {connection between the revoluble members 2I and 22, and the said members then travel in unison; I havefound' that in ordinary practice asliplof less than three hundredths of wound'a coil III of suitable insulated copper- 1 wire. This coil is insulatedby meansof insula tion II2 from the wallsof the groovelfl. ,The; ends of this coil pass through"suitablefholes drilled in the flange 92- and are connected to the collector ring 44 and to another collector ring I I3, also mounted on the insulating "ring t6, pre- A brush II4 contacts-withthe ring II3. A suitable switch is connected in viously referred to.

the lead from the brush H4 and also a rheostat similar to that previously described. Both of the leads from the brushes H4 and 41 may be connected to the same side of the power-line used for energizing the various coils with direct current, and a single lead from the brush 48 is connected to the other side of the power line. .In this manner the coils 42 and the clutch coil III 10 the maximumspeed obtainable through the elecv tr'omagnetic drive to the speed of the driving one per cent can be procured at full load.

If," on the other hand, gradual change from [shaft is desired, the rheostat used in conjunction withthewinding III isutilized. As the current in the winding III is gradually reduced, the heavier of the shoes 99 are first released through the action of centrifugal force and engage the .1

I Thus a. force less than that procured by all of the shoes ring 94 to produce partial clutching.

is obtainable and the slip between the members 2 I and 22 is partially reduced. As the current in the winding III isiurther reduced the other shoes are'brought into action and when the current is finally shut on all of the shoes act as may be separately energized and controlled as desired. Since the lugs 96 are constructed of non-magpreviously described to substantially lock the members 2 I- and 22 together. In either case when the members -2I and 22 are travelingin unison,

thecoils 42 are disconnected from the source of netic material, a magnetic path is formed through the flanges BI and 92 of annulus 81,-the

air gap between the surfaces I91 and H18 andthe part I92 of the shoe body I 00 which causes'the 2 shoes to be attracted by the annulus whencoil III. is energized.

In the operation of my invention, coil II I is first energized. This causes'the two flanges 9i and 92, which serve as poles-of an electromagnet, to draw the shoes 99 toward the same so that the surfaces I ll! of said shoes engage the surfaces I08 of the flanges SI and 92. This disengages the facings I05 from the friction surface 95 of ring 94. The shaft 23 is then'driven from the source of mechanical power from which variable speed is desired. This source may be a prime mover, such as a synchronous motor, or any other source of rotating mechanical power. After the shaft 23 has been brought up, to its required speed, the coils 42 on thecore structure are energized by passing current through the brushes 5? and. The current so provided is controlled as previously explained. Due to the rotation of the core structure 39, alternating current is induced in the squirrel cage bars 65. This produces torque between the two members, and

thereby the shaft 24 is caused 'to' 'rotate with; the-shaft 23. .As the current'delivered to the.

means is,"however, only in; the vicinity of 95%- to 97% of the speed of the shaft 23. Where it becomes desirable to run the shaft 23 at the same speed as'the'shaft 23, the clutch 83 is employed. While the coils a: are still energized, the current in the winding ii! is reduced. If this current is reduced rapidly or shut on instantaneously, the

attractive force of the magnet formed by the connected to the load and'must'start the load from rest. By means of my invention the load.

energy. It will. thus beseen" that no electrical energy is used when the shafts travel in unison.

The advantages of my invention are manifest.

By means of the construction disclosed the electromagnetic drive may be used to procure any speed upto substantially the speed of the driving member. When the driven member is connected to the driving member through the clutch employed, no exciting current is used either for the electromagnetic drive or for the clutch. Inasmuch as the load isusually driven for the greatest length of time at full speed it'will thus become apparent that my invention is economical since no current is consumed at full speed. .When, however, a condition arises in which a speed less than full speed is desired the same can be readily and easily procured. With my invention the load can be started fromsrest with a minimumamount of power and gradually brought uputo any desired speed including. the; speed oi the driving member, It will thus ,become apparent that power units of less capacity will be required than where the motor or other power unit is directly may be operated continuously at any desired speed within the limits of the drive. By means of the lugs employed for engagement-with the clutch shoes the shoes are freely movable in a radial direction and are restrained from move ment in a lateral directionand in a peripheral direction. Thus the shoes readily accommodate themselves to the contour ;of the surface of the ringwith which they engage and compensate for misalignment of the shafts and other irregulari ties in the construction and assembly of the parts. By employing shoes of difierent weights, either rapid or gradual acceleration to maximum speed can be procured. By properly selecting the weights of the shoes the clutch can be used for overload purposes, the clutch commencing to slip 7 when the load exceeds that desired.

Changes in the specific form of my invention, as herein disclosed, may be madewithin the scope of what is claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

1. A clutch comprising two relatively rotatable members, one of said members having an inwardly facing friction surface, the other of said members having an annulus of magnetic material U-shaped in cross section to provide an annular groove extending about the same, a coil in said groove, a clutch shoe of magnetic material overlying said annulus and adapted to be attracted to the same, means for holding said clutch shoe in position relative to said annulus, and a facing on said clutch shoe for engagement with said surface, said shoe being adapted to be moved outwardly by centrifugal force due to its own weight to procure engagement of said facing with said surface.

2. A clutch comprising two relatively rotatable members one of said members having an inwardly facing friction surface, the other of said members having an annulus of magnetic material U-shaped in cross section to provide an annular groove extending about the same, a coil in said groove, a clutch shoe of magnetic material overlying said annulus and adapted to be attracted to the same, lugs extending outwardly from said annulus, said shoe engaging said lugs and being restrained from movement circumferentially of said annulus thereby, and a facing on said shoe for engagement with said surface, said shoe being adapted to be moved outwardly by contrifugal force'due to its own weight to procure engagement of said facing with said surface.-

3. A clutch comprising two relatively rotatable members, one of said members having an inwardly facing friction surface, the other of said members having an annulus of magnetic material U-shaped in cross section to provide an annular groove extending about the same, a coil in said'groove, a clutch shoe of magnetic material overlying said annulus and adapted to be attracted to the same, lugs extending outwardly from said annulus, said clutch shoe engaging said lugs and being restrained from movement circumferentially of said annulus thereby, ears on said shoe for engagement with said lugs for restraining said shoe from lateral movement, and a facing on said shoe for engagement with said surface, said shoe being adapted to be moved outwardly by centrifugal force to procure engagement of said facing with said surface.

4. A clutch comprising two relatively rotatable members, one of said members having an inwardly facing friction surface, the other of said members having an annulus of magnetic material U-shaped in cross section to provide an annular groove extending about the same, and to provide spaced flanges on opposite sidesof said grooves formed with surfaces facing said first named surface, a clutch shoe constructed of magnetic material overlying the surfaces of said flanges, circumferentially spaced lugs extending members having an annulus of magnetic material U-shaped in cross section to provide an annular groove extending about the same, and to provide spaced flanges on opposite sides of said grooves formed with surfaces facing said first named surface, a clutch shoe constructed of magoutwardly from said flanges, the lugs on one flange being disposed opposite the lu s on the other flange, the ends of said shoe engaging said lugs, earns on the ends of said shoes for engagement between said lugs, and a facing on said shoe for engagement with said first named surface, said shoe being adapted to be moved outwardly by centrifugal force to procure engagement of said facing with said first named surface.

5. A clutch comprising two relatively rotatable members, one of said members having an inwardly facing friction surface, the other of said netic material overlying the surfaces of said flanges, circumferentially spaced lugs extending outwardly from said flanges, the lugs on one flange being disposed opposite the.- lugs on the other flange, said lugs being constructed of nonmagnetic material, the ends of said shoe engaging said lugs, ears on the ends of said shoes for engagement between said lugs, and a. facing on said shoe for engagement with first said named surface, said shoe being adapted to be moved outwardly by centrifugal force to procure engagement of said facing with said first named surface.

6. A clutch comprising two relatively rotatable members, one of said members having an inwardly facing friction surface, the other of said members having an annulus of magnetic material U-shaped in cross section to provide an annular groove extending about the same, a coil in said groove, a clutch shoe of magnetic material overlying said annulus and adapted to be attracted to the same, the body of said clutch shoe being constructed of two separable parts adapted to receive a shim therebetween, means for holding said parts detachably connected together, means for holding said clutch shoe in position relative to said annulus, and a facing on said shoe for engagement with said surface, said shoe being adapted to be moved outwardly by centrifugal force to procure engagement of the facing with said surface, said shim being arcuate and being situated concentrically with the engaging surface of said facing.

7. In combination, a rotatable driving member, a rotatable driven member, an internal friction surface on one of said members, an annulus on the other of said members within said internal friction surface, a plurality of shoes carried by said annulus and movable radially outward therefrom by centrifugal force into engagement with said friction surface, and electro-magnetic means within said friction surface and carried by said annulus for variably restraining such outward movement of said shoes.

8. A variable speed drive-comprising a rotatable driving member, a rotatable driven member, an internal friction surface on one of said members, a plurality of shoes of different weight carried by the other of said members and independently movable outward therefrom by centrifugal force into engagement with said friction surface, and means for successively restraining such outward movement of said shoes while said members are rotating to procure successive engagement of the shoes with the friction surface.

9. In combination, a rotatable driving member, a rotatable driven member, one of said members having an annular portion providing an internal friction surface, an annulus on the other of said members within said internal friction surface,

' said annulus having U-shaped cross section to faces of said flanges, means on said annulus for restraining relative rotation between said shoe and annulus, said shoe being adapted to be moved outwardly by centrifugal force. and a coil within constructed of magnetic material overlying the surfaces of said flanges, means on said annulus for restraining relative rotation between said shoe and annulus, said shoe being adapted to be moved outwardly by centrifugal force, a coil within said annulus for moving said shoe radially inwardly away from said friction surface, and means for varying the'current flowing through said coil to vary the frictional engaging forcebetween said shoe and friction surface.

CHARLES T. HIBBARD. 

